JP5729611B2 - Method for producing metallic molybdenum coating film - Google Patents

Description

The present invention relates to the production how the molybdenum metal coating film.
Specifically, a metal molybdenum coating film having excellent adhesion and film strength and high conductivity is formed by a coating method in which a coating solution for forming a metal molybdenum coating film is applied, dried, and fired on a heat-resistant substrate such as glass. The present invention relates to a metal molybdenum coating film manufacturing method and a metal molybdenum coating film obtained by the manufacturing method.

In recent years, a metal molybdenum film is used for a back electrode of a chalcopyrite thin film solar cell, and a wiring electrode of a liquid crystal display, a touch panel or the like.
Here, the chalcopyrite thin-film solar cell has been actively developed in recent years because of its high conversion efficiency, and its structure is such that a back electrode layer of metallic molybdenum (Mo) is formed on a substrate such as glass. A chalcopyrite semiconductor photoelectric conversion layer mainly composed of Cu, In, Ga, and Se is formed on the back electrode layer, and a buffer layer such as CdS and a ZnO-based (for example, aluminum oxide doped) are further formed thereon. Thus, a transparent electrode layer of zinc oxide (AZO) is sequentially formed (see, for example, Patent Documents 1 and 2).

The reason why metal molybdenum is used as the back electrode material of this chalcopyrite thin film solar cell is that metal molybdenum is not necessarily optimal from the viewpoint of conductivity, but chalcopyrite semiconductor photoelectric conversion layer (for example, CuInSe ₂ ) and This is because it is relatively difficult to react and is easily available.
And as a manufacturing method of this metal molybdenum back electrode layer (metal molybdenum film), vapor deposition methods (vapor phase method) such as vacuum vapor deposition, sputtering, and chemical vapor deposition are widely used (for example, patent documents). 1 and 2).

Although these methods can form a dense metal molybdenum film with excellent conductivity on a substrate, the film forming apparatus used for forming the metal molybdenum film is based on a vacuum vessel. Therefore, it is very expensive, and the component gas pressure in the manufacturing apparatus must be precisely controlled every time the substrate is formed, so there is a problem in manufacturing cost and mass productivity.
Therefore, there has been a demand for a method for forming a high-quality metal molybdenum film on a substrate by a simple method and at a low cost.

JP 2000-91601 A Specification of WO2005 / 109525

In view of such circumstances, the present invention provides a low-cost and simple method for producing a metal molybdenum film, which has excellent adhesion and film strength and high conductivity by an ink coating method using a coating liquid containing an organic molybdenum compound. sex providing manufacturing how the metallic molybdenum coating film having also aims.

In view of the above problems, the inventors have conducted extensive research on a coating film obtained by applying, drying, and heat-treating a coating solution containing an organic molybdenum compound as a main component, and as a result, during the heat treatment, in mineralization of organic molybdenum compounds, lower molybdenum oxide having a deep blue membrane color; by forming the _{(MoO x 2 ≦ x <3} ), a lower molybdenum oxides in the subsequent reduction treatment (MoO x; ₂ ≦ x It was found that the reduction from <3) to metallic molybdenum can easily proceed to form a metallic molybdenum coating film having metallic luster. Furthermore, it has been found that the metal molybdenum coating film obtained by this method has both high conductivity, excellent adhesion and film strength, and the present invention has been completed.

That is, the first invention of the present invention is a coating process for forming a coating film by coating a coating solution for forming a metal molybdenum coating film containing an organic molybdenum compound as a main component on a heat-resistant substrate. Formed through each step of a drying process for drying to form a dry coating film, and a heating reduction process for forming a metal fine particle layer mainly composed of metal molybdenum by mineralizing and reducing the dry coating film by heat treatment. In the method for producing a metal molybdenum coating film, the heat reduction step first performs a heat treatment at 250 to 350 ° C. on the dry coating film mainly composed of the organic molybdenum compound formed in the drying step, _{a; (2 ≦ x <3 MoO} x) mainly composed of organic components contained in the dry coating film pyrolysis or combustion, or thermal decomposition and lower molybdenum oxide by mineralization was removed by combustion After genus oxide fine particles to form a metal oxide fine particle layer was densely filled, further subjected to reduction treatment heated to 450 ° C. or higher in a reducing atmosphere, the lower molybdenum oxide (MoO x; ₂ ≦ x < 3) A method for producing a metal molybdenum coating film, which is a step of forming a metal fine particle layer in which metal fine particles containing metal molybdenum as a main component are densely filled by reducing 3).

In the second invention of the present invention, the organic molybdenum compound in the first invention is acetylacetone molybdenum (molybdenum (VI) oxide bis-2,4-pentanedionate) [MoO ₂ (C ₅ H ₇ O ₂ ) ₂ ]. This is a method for producing a metal molybdenum coating film.

  According to a third aspect of the present invention, the reducing atmosphere in the first or second aspect is an atmosphere composed of hydrogen gas or a neutral gas containing at least one of hydrogen gas or organic solvent vapor, A method for producing a metal molybdenum coating film, wherein the reactive gas is at least one of nitrogen gas and inert gas.

  According to a fourth aspect of the present invention, there is provided an ink jet printing method, a screen printing method, or a gravure printing method, wherein a coating solution for forming a metal molybdenum coating film in the coating process in the first to third inventions is applied to a heat resistant substrate. , Offset printing method, flexographic printing method, dispenser printing method, slit coating method, die coating method, doctor blade coating method, wire bar coating method, spin coating method, dip coating method, spray coating method This is a method for producing a metal molybdenum coating film.

According to the method for producing a metal molybdenum coating film of the present invention, lower molybdenum oxide (MoO _x ; 2 ≦ x <3) having a deep blue film color is formed in the inorganicization of the organic molybdenum compound during the heat treatment. By doing so, since the reduction from lower molybdenum oxide (MoO _x ; 2 ≦ x <3) to metal molybdenum can be easily advanced in the subsequent reduction treatment, a metal molybdenum coating film having a metallic luster can be formed. A metal molybdenum coating film having high conductivity and excellent adhesion and film strength can be formed at low cost.

  Furthermore, the metal molybdenum coating film according to the present invention can be applied to various devices. When the metal molybdenum coating film is applied as an electrode layer, the heat resistant substrate on which the metal molybdenum coating film of the present invention is formed. Is suitable for power generation devices such as solar cells, display devices for liquid crystal displays (liquid crystal elements), input devices such as touch panels, and the like.

It is a figure which shows the relationship between saturated water vapor content (volume%) in air, and dew point temperature (degreeC). It is a figure which shows the reflection profile of the metal molybdenum coating film which concerns on Example 1, and the molybdenum oxide coating film which concerns on the comparative example 1. FIG.

Hereinafter, embodiments of the present invention will be described in detail.
The method for producing a metal molybdenum coating film of the present invention comprises a metal molybdenum coating film formed by coating a coating solution for forming a metal molybdenum coating film containing an organic molybdenum compound as a main component on a heat resistant substrate, drying, and heat reduction. In the manufacturing method of the above, a metal fine particle layer in which metal fine particles mainly composed of metal molybdenum are densely filled is formed. Thus, in the obtained metal molybdenum coating film, adhesion to the substrate, film strength, conductivity, etc. Improvement can be achieved, and cost reduction can be achieved by a simple manufacturing method.

[Metal molybdenum coating film structure]
First, the structure of the metal molybdenum coating film will be described.
For example, when a metal molybdenum film is formed by using a vapor phase growth method such as sputtering, a polycrystalline metal molybdenum film structure is usually formed, which is a film structure in which crystal grains of metal molybdenum are arranged through grain boundaries. In the film structure, metal molybdenum fine particles are hardly observed.

  On the other hand, in a metal molybdenum coating film formed by a coating method in which a coating solution for forming a metal molybdenum coating film mainly composed of the organomolybdenum compound of the present invention is applied to a heat resistant substrate, dried, and heated and reduced, the metal molybdenum fine particles are usually used. It has a film structure in which the metal molybdenum particles are bonded to each other, and the size of the metal molybdenum fine particles and the size of the voids existing between the metal molybdenum fine particles vary depending on the conditions of the heat reduction process, but are not limited to open pores (open pores). This is a metal molybdenum coating film composed of metal molybdenum fine particles having a surface.

  In such a metal molybdenum coating film, the metal molybdenum fine particles are densely filled, and at the same time, the crystal growth of the metal molybdenum fine particles is promoted, so that the metal molybdenum fine particles have small open pores (open pores) and are dense. It is necessary to form a film structure having a reinforced metal fine particle layer, which makes it possible to improve the conductivity and film strength of the metal molybdenum coating film.

  That is, the metal fine particle layer in which the metal molybdenum fine particles are densely packed in the present invention is appropriately subjected to the mineralization or reduction treatment conditions during the heat treatment in the coating method using the coating liquid for forming the metal molybdenum coating film. It is formed by setting.

The formation mechanism of the metal fine particle layer densely filled with such metal molybdenum fine particles is not yet clear, but in the present invention, in the mineralization of the organomolybdenum compound during the heat treatment, the film color once dark blue A lower molybdenum oxide (MoO _x ; 2 ≦ x <3) is formed, and the lower molybdenum oxide (MoO _x ; 2 ≦ x <3) is reduced in a subsequent reduction treatment to form a metal molybdenum coating film. Therefore, the densification of the metal oxide fine particle layer mainly composed of lower molybdenum oxide obtained by mineralization leads to the densification of the metal fine particle layer mainly composed of metal molybdenum. Conceivable.

[Metal molybdenum coating film coating solution]
Next, the coating liquid for forming a metal molybdenum coating film used in the present invention will be described in detail.
In the present invention, a metallic molybdenum coating film-forming coating solution containing an organic molybdenum compound as a main component is used, and after passing through a lower molybdenum oxide (MoO _x ; 2 ≦ x <3), metallic molybdenum is formed. is there.

First, a coating solution for forming a metal molybdenum coating film containing an organic molybdenum compound as a main component and containing an organic solvent will be described below.
As the organomolybdenum compound of the organometallic compound used in the present invention, for example, acetylacetone molybdenum as a molybdenum acetylacetone complex (formal name: molybdenum (VI) oxide bis-2,4-pentanedionate [MoO ₂ (C ₅ H ₇ O ₂ ) ₂ ]), molybdenum ethoxide as molybdenum alkoxide [Mo (C ₂ H ₅ O) ₅ ], and the like. Basically, it dissolves in a solvent and is subjected to chlorine gas or nitrogen oxide during heat treatment. Any organic molybdenum compound that does not generate a harmful gas such as gas and decomposes into a lower molybdenum oxide (MoO _x ; 2 ≦ x <3) by mineralization by heat treatment may be used, and among these, acetylacetone molybdenum is preferable.

The organomolybdenum compound contained in the coating solution for forming the metal molybdenum coating film is a main compound raw material for forming the metal molybdenum coating film on the heat-resistant substrate, and the content thereof is in the range of 1 to 30% by weight. Is preferable, and more preferably 5 to 20% by weight.
If the total content is less than 1% by weight, only a thin metal molybdenum coating film can be obtained, and sufficient conductivity cannot be obtained. On the other hand, if it exceeds 30% by weight, the organomolybdenum compound in the coating solution for forming the metal molybdenum coating film is likely to be precipitated and the stability of the coating solution is lowered, or the resulting metal molybdenum coating film becomes too thick and cracks ( Cracks) may occur.

  In order to improve the function of the metal molybdenum coating film, a small amount of organic sodium compound, organic titanium compound, organic zirconium compound, organic hafnium compound, organic vanadium compound, organic niobium compound is added to the coating liquid for forming the metal molybdenum coating film, as necessary. Any one or more of an organic tantalum compound and an organic tungsten compound may be added.

  Furthermore, an organic binder may be added to the coating solution for forming the metal molybdenum coating film, if necessary. By adding the organic binder, the wettability with respect to the heat-resistant substrate is improved, and at the same time, the viscosity of the coating solution can be adjusted. The organic binder is preferably a material that burns or thermally decomposes during heat treatment, and cellulose derivatives, acrylic resins, and the like are effective as such materials.

Examples of cellulose derivatives used in organic binders include methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, ethyl hydroxyethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, carboxyethyl methyl cellulose, and nitrocellulose. Among these, hydroxypropyl cellulose (hereinafter sometimes referred to as “HPC”) is preferable.
In addition, many types of cellulose derivatives and acrylic resins having different molecular weights are commercially available. For example, HPC has a high molecular weight type, a medium molecular weight type, and a low molecular weight type depending on the molecular weight. As the molecular weight increases, the viscosity of the coating solution for forming a metal molybdenum coating film blended as a binder can be increased. The selection of the molecular weight type and the determination of the blending amount must be optimized from time to time depending on the coating properties of the coating solution for forming the metal molybdenum coating film and the coating method and coating thickness of the coating solution for forming the metal molybdenum coating film. is there.

If the above HPC is used, sufficient wettability can be obtained at a content of 5% by weight or less, and at the same time, the viscosity can be greatly adjusted. The combustion start temperature of HPC in the atmosphere is about 300 ° C., and combustion occurs when the heat treatment in the heat reduction process is performed in the temperature range of 300 to 350 ° C. Therefore, lower molybdenum oxide (MoO _x ; It is possible to finally produce a metal molybdenum coating film having good conductivity without inhibiting the growth of metal oxide fine particles mainly composed of ≦ x <3). When the content of HPC is more than 5% by weight, it becomes gelled and tends to remain in the coating solution, forming a very porous metal molybdenum coating film, and the transparency and conductivity are significantly impaired.
Here, as the cellulose derivative, for example, when ethyl cellulose is used instead of HPC, the viscosity of the coating solution can be set lower than when HPC is used. However, in the screen printing method or the like in which a high viscosity coating solution is suitable. Pattern printability is slightly reduced.

By the way, although nitrocellulose is excellent in thermal decomposability, harmful nitrogen oxide gas is generated during the heat treatment, which may cause problems in deterioration of the heat treatment furnace and exhaust gas treatment. As described above, the cellulose derivative to be used needs to be appropriately selected depending on the situation.
The acrylic resin is preferably an acrylic resin that burns at a relatively low temperature.

  In addition, the coating solution for forming a metal molybdenum coating film has a very small amount (for example, 0.001 to 0.05% by weight with respect to the coating solution for forming a metal molybdenum coating film) for the purpose of improving coating properties and film uniformity. ) Surfactant (polymer surfactant, silicone surfactant, etc.) may be added.

  Examples of the organic solvent contained in the coating solution for forming the metal molybdenum coating film include N-methyl-2-pyrrolidone (NMP) and acetylacetone, which can dissolve an organic molybdenum compound (molybdenum acetylacetone complex compound) at a high concentration, or a mixed solvent thereof. Is preferred.

  Furthermore, in order to adjust the coating solution to a low viscosity or improve the coating properties, the solvent mixed in the coating solution for forming the metal molybdenum coating film is a solution in which various organometallic compounds and cellulose derivatives or acrylic resins are dissolved. And solvents other than the above include water, methanol (MA), ethanol (EA), 1-propanol (NPA), isopropanol (IPA), butanol, pentanol, benzyl alcohol, diacetone alcohol ( DAA) alcohol solvents, acetone, methyl ethyl ketone (MEK), methyl propyl ketone, methyl isobutyl ketone (MIBK), ketone solvents such as cyclohexanone, isophorone, ethyl acetate, butyl acetate, isobutyl acetate, amyl formate, isoamyl acetate, Butyl propionate, isopropyl butyrate, Ethyl acetate, butyl butyrate, methyl lactate, ethyl lactate, methyl oxyacetate, ethyl oxyacetate, butyl oxyacetate, methyl methoxyacetate, ethyl methoxyacetate, butyl methoxyacetate, methyl ethoxyacetate, ethyl ethoxyacetate, methyl 3-oxypropionate , Ethyl 3-oxypropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl 2-oxypropionate, ethyl 2-oxypropionate, Propyl 2-oxypropionate, methyl 2-methoxypropionate, ethyl 2-methoxypropionate, propyl 2-methoxypropionate, methyl 2-ethoxypropionate, ethyl 2-ethoxypropionate, 2-oxy-2-methyl Methyl lopionate, ethyl 2-oxy-2-methylpropionate, methyl 2-methoxy-2-methylpropionate, ethyl 2-ethoxy-2-methylpropionate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, aceto Esters such as methyl acetate, ethyl acetoacetate, methyl 2-oxobutanoate, ethyl 2-oxobutanoate, ethylene glycol monomethyl ether (MCS), ethylene glycol monoethyl ether (ECS), ethylene glycol isopropyl ether (IPC), ethylene Glycol monobutyl ether (BCS), ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol methyl ether (PGM), propylene glycol Ethyl ether (PE), propylene glycol methyl ether acetate (PGM-AC), propylene glycol ethyl ether acetate (PE-AC), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether Glycols such as acetate, diethylene glycol monobutyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether Derivatives, benzene derivatives such as toluene, xylene, mesitylene, dodecylbenzene, cresols, xylenol, ethylphenol, p-tert-butylphenol, octylphenol, nonylphenol, alkylphenols such as cashew nut shell liquid [3 pentadecadedecylphenol] or Alkenylphenol solvents, dibasic acid esters such as succinic acid esters, glutaric acid esters, adipic acid esters, malonic acid esters, phthalic acid esters (eg, dibasic acid dimethyl, dibasic acid diethyl, etc.) solvents, formamide (FA) , N-methylformamide, dimethylformamide (DMF), dimethylacetamide, dimethylsulfoxide (DMSO), ethylene glycol, diethylene glycol, propylene glycol , Dipropylene glycol, 1,3-butylene glycol, pentamethylene glycol, 1,3-octylene glycol, tetrahydrofuran (THF), chloroform, mineral spirits, terpineol, etc., and some mixtures thereof, It is not limited to these.

  Considering the stability of the coating solution and the film formability, the solvent used is preferably methyl ethyl ketone (MEK), cyclohexanone, propylene glycol monomethyl ether (PGM), γ-butyrolactone, or the like.

  The coating solution for forming a metal molybdenum coating film used in the present invention is obtained by adding a small amount of any one or more of various organic metal compounds other than these to the above organic molybdenum compound, and further adding an organic binder as necessary. It is produced by heating and dissolving the mixture in a solvent.

The heating and melting at the time of producing the coating solution for forming the metal molybdenum coating film is usually performed by setting the heating temperature to 60 to 180 ° C. and stirring for 0.5 to 12 hours.
When the heating temperature is lower than 60 ° C., it does not dissolve sufficiently. For example, in the case of a coating solution for forming a metal molybdenum coating film containing acetylacetone molybdenum as a main component, precipitation and separation of acetylacetone molybdenum and the like occur and the coating solution is stable. When the temperature is higher than 180 ° C., the evaporation of the solvent becomes remarkable and the composition of the coating solution changes, which is not preferable.

  The viscosity of the coating solution for forming a metal molybdenum coating film can be adjusted depending on the molecular weight and content of the organic binder contained, and the type of solvent, so that the inkjet printing method, screen printing method, gravure printing method, offset printing method, flexographic printing method, etc. The viscosity can be adjusted to suit each application method such as printing method, dispenser printing method, slit coating method, die coating method, doctor blade coating method, wire bar coating method, spin coating method, spray coating method, etc. it can.

  A coating solution having a high viscosity (about 5000 to 50000 mPa · s) can be prepared by containing a high molecular weight organic binder in an amount of 5% by weight or less, preferably 2 to 4% by weight. On the other hand, the low-viscosity (about 5 to 500 mPa · s) coating solution contains 5% by weight or less, preferably 0.1 to 2% by weight of a low molecular weight organic binder, and is diluted with a low viscosity diluent. Can be produced. Further, the medium viscosity (500 to 5000 mPa · s) coating solution is prepared by mixing a high viscosity coating solution and a low viscosity coating solution.

[Method for producing metal molybdenum coating film]
The manufacturing method of the metal molybdenum coating film of the present invention will be described in detail.
The metal molybdenum coating film of the present invention is a coating process in which a coating solution for forming a metal molybdenum coating film is applied on a heat resistant substrate to form a coating film, a drying process in which the coating film is dried to form a dry coating film, The dried coating film is mineralized and reduced by heat treatment to form a heat reduction process for forming a metal film containing metal molybdenum as a main component.

(A) Coating process Coating of a coating solution for forming a metal molybdenum coating film on a heat-resistant substrate is performed by inkjet printing, screen printing, gravure printing, offset printing, flexographic printing, dispenser printing, slit coating. It is applied using various coating methods such as a die coating method, a doctor blade coating method, a wire bar coating method, a spin coating method, and a spray coating method.
These coatings are preferably performed in a clean atmosphere such as a clean room where the temperature and humidity are controlled. The temperature is generally room temperature (about 25 ° C.) and the humidity is generally 40 to 60% RH.

As the heat-resistant substrate, oxide-based inorganic substrates such as soda lime glass, non-alkali glass, and quartz glass, and metal-based inorganic substrates such as stainless steel, aluminum (Al), nickel (Ni), and copper (Cu) are used. Can be used.
Moreover, what formed the metal conductive film (stainless steel, Al, Ni, Cu, etc.) on the said various oxide type inorganic board | substrates using sputtering method, vapor deposition method, the plating method, etc. is good also as a heat resistant board | substrate. In this case, the metal molybdenum coating film of the present invention is formed on the metal conductive film. When the substrate having such a film structure is applied to, for example, the above-described chalcopyrite thin film solar cell, the metal molybdenum coating film is between the chalcopyrite semiconductor photoelectric conversion layer (for example, CuInSe ₂ ) and the metal conductive film. It functions as a reaction preventing electrode layer (diffusion barrier electrode layer).

(B) Drying step In the next drying step, the heat-resistant substrate coated with the coating solution for forming a metal molybdenum coating film is usually applied at 80 to 180 ° C. in the atmosphere for 1 to 30 minutes, preferably 2 to 10 minutes. The film is dried to produce a dry coating film.
The drying conditions (drying temperature, drying time) may be appropriately selected depending on the type of heat-resistant substrate to be used, the coating thickness of the coating solution for forming a metal molybdenum coating film, and the like, and are not limited to the above drying conditions. However, in consideration of productivity, it is desirable that the drying time is shortened to the minimum necessary so that the quality of the obtained dry coating film is not deteriorated.

In addition, it is also possible to apply reduced-pressure drying (attainment pressure: usually 1 kPa or less) instead of drying in the air as necessary. In this drying under reduced pressure, the solvent in the applied coating liquid for forming a transparent conductive film is forcibly removed under reduced pressure and the drying proceeds, so that drying in a shorter time is possible compared to drying in the air. Therefore, it can be useful for shortening the processing time of the manufacturing process.
The produced dry coating film is obtained by volatilizing and removing an organic solvent from a coating solution for forming a metal molybdenum coating film. An organic molybdenum compound, a small amount of an organic metal compound, an organic binder, and the like are added as necessary. It is composed of organic components.

(C) Heat reduction process In the heat reduction process, first, a dry coating film produced in the drying process is heat-treated to form an organomolybdenum compound in the dry coating film, or various organometallic compounds added in small amounts as necessary. Organic molybdenum components containing bismuth and organic components such as organic binder added as necessary are mineralized by thermal decomposition and combustion (oxidation) to produce lower molybdenum oxide (MoO _x ; 2 ≦ x <3) A metal oxide fine particle layer densely filled with metal oxide fine particles as a main component is formed.
Next, the metal oxide fine particle layer mainly composed of the lower molybdenum oxide (MoO _x ; 2 ≦ x <3) is heated to 450 ° C. or more in a reducing atmosphere, and the lower molybdenum oxide (MoO _x ; 2 ≦ x <3) is reduced to form a metal fine particle layer densely filled with metal fine particles mainly composed of metal molybdenum. The metal fine particle layer (metal molybdenum coating film) contains oxygen (O) accompanying the surface oxidation of a small amount of metal fine particles and carbon (C) that could not be completely removed from the metal fine particle layer as impurity elements. However, it does not significantly impair the function of the membrane.

That is, in the mineralization of the heat reduction process, when the heating temperature is increased to 250 to 350 ° C. in the temperature raising process, regardless of the presence or absence of oxygen in the atmosphere (for example, regardless of the air atmosphere or the hydrogen-containing atmosphere) ) The above-mentioned organomolybdenum compounds in dry coating films (including those containing various organometallic compounds added in small amounts) are gradually pyrolyzed and burned (oxidized) to form a lower molybdenum oxide having a dark blue film color. Conversion (so-called mineralization) to (MoO _x ; 2 ≦ x <3) occurs.

Here, the lower molybdenum oxide (MoO _x ; 2 ≦ x <3) having a deep blue film color is a colorless and transparent molybdenum oxide when heated at a temperature exceeding 350 ° C. in an oxygen-containing atmosphere such as air. It is oxidized to (MoO ₃ ) (also known as molybdenum trioxide), and this molybdenum oxide (MoO ₃ ) is not reduced to metallic molybdenum even if the temperature is raised to 450 ° C. or higher (for example, about 500 ° C.) in a reducing atmosphere. Therefore, a metal molybdenum coating film cannot be obtained. Therefore, after the lower molybdenum oxide (MoO _x ; 2 ≦ x <3) is once formed by mineralization by heat treatment at 250 to 350 ° C., the atmosphere is used to prevent oxidation to molybdenum oxide (MoO ₃ ). In a reducing atmosphere, and it is necessary to raise the temperature to 450 ° C. or higher in the reducing atmosphere. As a result, the lower molybdenum oxide (MoO _x ; 2 ≦ x <3) is easily reduced to metallic molybdenum. A coating film can be obtained.

In the coating liquid for forming a metal molybdenum coating film containing an organic binder, it is desirable to remove the organic binder from the coating film by thermal decomposition / combustion (oxidation), etc., at the time of mineralization in the heat reduction process. Although depending on the type of organic binder used, an oxygen-containing atmosphere (for example, air) is generally preferable. Usually, the organic binder is gradually pyrolyzed and burned (oxidized) during heat treatment at 250 to 350 ° C. for mineralization, and is mainly converted into carbon dioxide (CO ₂ ) and moisture (H ₂ O). In order to volatilize in the atmosphere and disappear from the film (for example, in the case of the above-mentioned HPC, it is almost disappeared by heat treatment at about 300 to 350 ° C. in the air). Finally, it hardly remains in the metal molybdenum coating film.

On the other hand, a coating solution for forming a metal molybdenum coating film that does not contain an organic binder does not require oxygen for the combustion (oxidation) of the organic binder, so it is reduced from the time of heat treatment at 250 to 350 ° C. for mineralization. A reducing atmosphere can be applied throughout the process. This is because the organic molybdenum compound itself can be mineralized by thermal decomposition even in a reducing atmosphere to produce a lower molybdenum oxide (MoO _x ; 2 ≦ x <3).

As described above, the formation mechanism of the metal fine particle layer in which such metal molybdenum fine particles are densely packed is not yet clear. However, in the present invention, in the mineralization of the organomolybdenum compound during the heat treatment, it is once concentrated. A lower molybdenum oxide (MoO _x ; 2 ≦ x <3) having a blue film color is formed, and then the lower molybdenum oxide (MoO _x ; 2 ≦ x <3) is reduced in a subsequent reduction treatment to apply metal molybdenum. Since the film is formed, the metal oxide fine particle layer mainly composed of lower molybdenum oxide obtained by mineralization is densified, and the metal fine particle layer mainly composed of metal molybdenum is finally densified. It is thought that it leads to.

Therefore, in the heat reduction step, first, the dry coating film prepared in the drying step is heat-treated, and the organomolybdenum compound in the dry coating film, or an organic molybdenum compound containing various organometallic compounds added in small amounts as necessary, And, if necessary, an organic component such as an organic binder added thereto is mineralized by thermal decomposition and combustion (oxidation), and a metal oxide mainly composed of lower molybdenum oxide (MoO _x ; 2 ≦ x <3) A metal oxide fine particle layer filled with fine particles is formed.
Therefore, in order to obtain a dense metal molybdenum coating film, it is necessary to densify the metal oxide fine particle layer whose main component is a lower molybdenum oxide (MoO _x ; 2 ≦ x <3) before the reduction treatment.

In order to densify the metal oxide fine particle layer mainly composed of this lower molybdenum oxide (MoO _x ; 2 ≦ x <3), the dew point temperature is used during the mineralization by the heat treatment at 250 to 350 ° C. It is desirable to apply an atmosphere having a low water content, that is, a low water vapor content.
Usually, the dew point temperature of a reducing gas such as hydrogen or a neutral gas such as nitrogen is sufficiently low (for example, −60 ° C. or lower), and there is no problem. However, air as an oxygen-containing atmosphere usually contains moisture. Therefore (for reference, FIG. 1 shows the relationship between the saturated water vapor content (volume%) in the air and the dew point temperature (° C.)), and a coating solution for forming a metal molybdenum coating film containing the above organic binder was used. In some cases, it is desirable to use an oxygen-containing atmosphere (such as air) having a low dew point temperature. In this case, a preferable dew point temperature is −10 ° C. or lower, more preferably −20 ° C. or lower, and further preferably −30 ° C. or lower.

As described above, the mechanism of dense filling of the metal oxide fine particles mainly composed of lower molybdenum oxide is not necessarily clear. For example, water vapor in the air atmosphere
(1) has an action of promoting thermal decomposition and combustion (oxidation) of the organic binder component intervening between the organic molybdenum compound and the lower molybdenum oxide;
(2) has an action of promoting crystallization of the lower molybdenum oxide itself and crystal growth;
As a result, in an atmosphere with a low dew point temperature, the film structure in which organic components (organic components of organic molybdenum compounds and organic binders) remain in the coating film is maintained until the initial stage of mineralization by heat treatment. This is presumed to be flexible due to the action of the organic component and to suppress the crystallization of the lower molybdenum oxide and to allow the film to shrink (densify) in the direction perpendicular to the heat resistant substrate.

  Examples of the oxygen-containing atmosphere gas that can be used in the mineralization of the present invention include air, oxygen gas, or a mixed gas of oxygen gas and neutral atmosphere gas (nitrogen, inert gas (argon, helium, etc.)). Inexpensive and readily available air is preferred.

  The reducing atmosphere used in the reduction treatment of the present invention is an atmosphere comprising hydrogen gas or the above neutral gas containing at least one of hydrogen gas or organic solvent vapor, and the neutral gas is nitrogen gas, inert gas Any one or more of gases (argon, helium, etc.) may be mentioned, but a neutral gas atmosphere containing hydrogen gas or hydrogen gas is preferred. Among them, a mixed gas of 1-4% hydrogen-99-96% nitrogen is a preferable atmosphere because there is no risk of explosion even if it leaks into the atmosphere.

The heating temperature during the reduction treatment in the heat reduction step is 450 ° C. or higher, preferably 500 ° C. or higher, at which the reduction of the lower molybdenum oxide (MoO _x ; 2 ≦ x <3) proceeds, and the heating time is preferably Is 5 to 120 minutes, more preferably 15 to 60 minutes.
Even if the reduction treatment is performed at a heating temperature lower than 450 ° C., the reduction reaction does not proceed sufficiently and a high-quality metal molybdenum coating film cannot be obtained.

  The upper limit of the heating temperature during the reduction treatment is not particularly limited, but it is affected by the type of heat treatment apparatus used in the heat reduction step and the heat resistance of the heat resistant substrate, and is the most commonly used soda lime glass substrate. Then, since the strain point is about 510 ° C., it is preferable to perform the heat treatment at a temperature lower than this temperature. However, if the soda lime glass substrate is heat-treated on a heat-resistant base material having higher heat resistance, the substrate can be relatively distorted, so that the heat treatment at about 600 ° C. is also possible. Of course, when a glass substrate with higher heat resistance such as a quartz glass substrate, an alkali-free glass substrate, or a high strain point glass substrate is used, a higher heating temperature can be applied.

Examples of the heat treatment apparatus used in the heat treatment step include, but are not limited to, a hot plate, a hot-air circulating heat treatment furnace, a far-infrared heating apparatus, and the like. However, in order to carry out the present invention, it is necessary to control the dew point temperature in the heat treatment atmosphere or to apply a reducing atmosphere. Therefore, the heat treatment apparatus to be used is a sealed type (gas replacement type) in which the heat treatment atmosphere can be controlled. ) Is required.
In addition, there is no restriction | limiting in particular about the temperature increase rate in the temperature increase process in the mineralization of a heat reduction process or a reduction process, However, It is the range of 5-40 degree-C / min, More generally, 10-30 degree-C / min. . If the heating rate is slower than 5 ° C / min, it takes too much time to raise the temperature and the efficiency is deteriorated. On the other hand, if a heating rate exceeding 40 ° C / min is attempted with the above heat treatment apparatus, the heater capacity increases. Too impractical.

The method for manufacturing a metal molybdenum coating film according to the present invention and the metal molybdenum coating film obtained by the manufacturing method include power generation devices such as solar cells, display devices for liquid crystal displays (liquid crystal elements), and input devices such as touch panels. Application to the electrode can greatly contribute to, for example, cost reduction of the device.
EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

[Preparation of coating solution]
Acetylacetone molybdenum (solid at room temperature) (formal name: molybdenum (VI) oxide bis-2,4-pentanedionate [MoO ₂ (C ₅ H ₇ O ₂ ) ₂ ] (molecular weight = 326.17) 10 g, N-methyl 2-Pyrrolidone (NMP) 7 g and acetylacetone 7 g Hydroxypropylcellulose (HPC; low molecular weight type) 1 g were mixed, heated to 120 ° C. and stirred for 120 minutes to dissolve.
Next, 25 g of the obtained solution was mixed with 25 g of cyclohexanone, 10 g of propylene glycol monomethyl ether (PGM), and 40 g of methyl ethyl ketone (MEK), and stirred well until uniform, and made of propylene (PP) having a pore size of 0.22 μm. Filtration with a filter produced a coating solution for forming a metal molybdenum coating film containing 10% by weight of acetylacetone molybdenum and 1% by weight of hydroxypropylcellulose. The viscosity (25 ° C.) of this coating solution for forming a metal molybdenum coating film was about 10 mPa · s.

[Production of metal molybdenum coating film]
The prepared coating solution for forming a metal molybdenum coating film was a 25 ° C. alkali-free glass substrate (10 cm × 10 cm × thickness 0.7 mm; visible light transmittance = 91.2%, haze value = 0.26%, refractive index = 1.52) After spin coating (500 rpm × 60 sec) on the entire upper surface, it was dried in an air atmosphere at 100 ° C. for 5 minutes using a hot air dryer, and further an air atmosphere having a dew point temperature of −55 ° C. using a hot plate. (3 liter / min supply; average flow rate of atmospheric gas on substrate = approximately 0.045 m / sec), the temperature was raised to 300 ° C. over 30 minutes (temperature increase rate: 10 ° C./min), and 30 ° C. at 30 ° C. min heat treatment to, mineralized by combustion and thermal decomposition of organic components such as acetylacetone molybdenum or HPC, lower molybdenum oxide having a deep blue membrane color; the _{(MoO x 2 ≦ x <3} ) main Min and metal oxide fine particles to form a metal oxide fine particle layer was densely filled.
Subsequently, the atmosphere is switched to a reducing atmosphere (3 vol% hydrogen-97 vol% nitrogen) (3 liter / min supply; average flow rate of atmospheric gas on the substrate = about 0.045 m / sec), 300 ° C. to 500 ° C. Is heated (heating rate: 10 ° C./min), subjected to a reduction treatment at 500 ° C. for 30 minutes, and lower molybdenum oxide (MoO _x ; 2 ≦ x <3) is reduced to contain metal molybdenum as a main component. A metal molybdenum coating film according to Example 1 consisting of a metal fine particle layer having a metallic luster and densely filled with metal fine particles was prepared.

[Characteristic evaluation]
Table 1 shows the manufacturing process conditions for the mineralization and reduction treatment of the metal molybdenum coating film and the film quality of the obtained film.
The surface resistance, film thickness, specific resistance value, visible light transmittance and haze value, film strength and adhesion properties of the produced metal molybdenum coating film were measured, and the results are shown in Table 2. Moreover, the reflection profile of the obtained metal molybdenum coating film according to Example 1 is shown in FIG. 2 together with the reflection profile of the molybdenum oxide coating film of Comparative Example 1.

The surface resistance of the metal molybdenum coating film was measured using a surface resistance meter Loresta AP (MCP-T400) manufactured by Mitsubishi Chemical Corporation.
The haze value and visible light transmittance were measured based on JIS K7136 (haze value) and JIS K7361-1 (transmittance) using a Nippon Denshoku Co., Ltd. haze meter (NDH5000).
The film thickness was measured using an optical profiler (New View 6200 manufactured by Zygo).
For film strength and adhesion, rub the coating film formed on the substrate with a nail and observe the appearance of the coating film, ◯ for those without scratches or peeling, and those with large scratches or significant peeling, respectively. Evaluated as “x”.
The reflection profile of the coating film was measured using a spectrophotometer (U-4000) manufactured by Hitachi, Ltd.
The visible light transmittance and the haze value are values only for the coating film, and were obtained by the following formulas (1) and (2), respectively.

[Preparation of coating solution]
Acetylacetone molybdenum (solid at room temperature) (formal name: molybdenum (VI) oxide bis-2,4-pentanedionate [MoO ₂ (C ₅ H ₇ O ₂ ) ₂ ] (molecular weight = 326.17) 10 g, N-methyl 2-Pyrrolidone (NMP) 7.5 g and acetylacetone 7.5 g were mixed, heated to 120 ° C. and stirred for 60 minutes to dissolve.
Next, 25 g of the resulting solution was mixed with 25 g of cyclohexanone, 10 g of propylene glycol monomethyl ether (PGM), 39.98 g of methyl ethyl ketone (MEK), and 0.02 g of a surfactant, and stirred well until uniform. The solution was filtered with a 0.22 μm propylene (PP) filter to prepare a coating solution for forming a metal molybdenum coating film containing no organic binder and 10% by weight of acetylacetone molybdenum. The viscosity (25 ° C.) of the coating solution for forming a metal molybdenum coating film was about 5 mPa · s.

[Production of metal molybdenum coating film]
The prepared coating solution for forming a metal molybdenum coating film was a 25 ° C. alkali-free glass substrate (10 cm × 10 cm × thickness 0.7 mm; visible light transmittance = 91.2%, haze value = 0.26%, refractive index = 1.52) After spin coating (500 rpm × 60 sec) on the entire upper surface, it was dried in an air atmosphere at 100 ° C. for 5 minutes using a hot air dryer, and further reduced atmosphere (3% by volume hydrogen −) using a hot plate. 97 volume% nitrogen) (3 liters / minute supply; average flow rate of atmospheric gas on substrate = approximately 0.045 m / second), heated to 500 ° C. over 50 minutes (temperature increase rate: 10 ° C./minute) The metal-molybdenum coating film according to Example 2 comprising a metal fine particle layer having a metallic luster in which metal fine particles mainly composed of metal molybdenum were densely packed by heat treatment at 500 ° C. for 30 minutes was produced.

Note that in the temperature increasing process up to 500 ° C. in the reducing atmosphere, the organic component of acetylacetone molybdenum is thermally decomposed and mineralized in a temperature range of 200 to 300 ° C., and a lower molybdenum oxide having a deep blue film color ( A metal oxide fine particle layer in which metal oxide fine particles mainly composed of MoO _x ; 2 ≦ x <3) are densely filled is formed, and further, lower molybdenum oxide (MoO) is gradually added in a temperature range of 450 to 500 ° C. It was confirmed that reduction of _x ; 2 ≦ x <3) to metal molybdenum progressed, and a metal fine particle layer having a metallic luster was formed.

  Table 1 shows the manufacturing process conditions for the mineralization and reduction treatment of the metal molybdenum coating film and the film quality of the obtained film. Further, various characteristics of the produced metal molybdenum coating film were measured in the same manner as in Example 1, and the results are shown in Table 2.

(Comparative Example 1)
Using the coating liquid for forming a metal molybdenum coating film of Example 1, the temperature was raised to 300 ° C. over 30 minutes (temperature increase rate: 10 ° C./min), and instead of heat treatment at 300 ° C. for 30 minutes, up to 500 ° C. The temperature was increased over 50 minutes (temperature increase rate: 10 ° C./min), and after heat treatment at 500 ° C. for 30 minutes, organic components such as acetylacetone molybdenum and HPC were made inorganic by combustion and thermal decomposition, and colorless and transparent molybdenum A metal oxide fine particle layer in which metal oxide fine particles mainly composed of oxide (MoO ₃ ) were densely filled was formed.

Subsequently, the atmosphere is switched to a reducing atmosphere (3 vol% hydrogen-97 vol% nitrogen) (3 liter / min supply; average flow rate of atmospheric gas on the substrate = approximately 0.045 m / sec), at 500 ° C. for 30 min. However, the reduction of molybdenum oxide (MO ₃ ) to metal molybdenum did not proceed, and the colorless and transparent metal was finely packed with metal oxide fine particles mainly composed of molybdenum oxide (MoO ₃ ). A molybdenum oxide coating film according to Comparative Example 1 having an oxide fine particle layer was produced.

  Table 1 shows the manufacturing process conditions for the inorganicization and reduction treatment of the molybdenum oxide coating film, and the film quality of the obtained film. Further, various characteristics of the manufactured molybdenum oxide coating film were measured in the same manner as in Example 1, and the results are shown in Table 2. The reflection profile of the molybdenum oxide coating film according to Comparative Example 1 obtained is shown in FIG. 2 together with the reflection profile of the metal molybdenum coating film of Example 1.

(Comparative Example 2)
Using the coating solution for forming a metal molybdenum coating film of Example 1, the temperature was increased to 300 ° C. over 30 minutes (temperature increase rate: 10 ° C./min), and instead of heat treatment at 300 ° C. for 30 minutes, up to 400 ° C. Heated over 40 minutes (temperature increase rate: 10 ° C./min) and heat-treated at 400 ° C. for 30 minutes. Organic components such as acetylacetone molybdenum and HPC burned and become inorganic, resulting in colorless and transparent molybdenum. A metal oxide fine particle layer in which metal oxide fine particles mainly composed of oxide (MoO ₃ ) were densely filled was formed.

Subsequently, the atmosphere is switched to a reducing atmosphere (3 vol% hydrogen-97 vol% nitrogen) (3 liter / min supply; average flow rate of atmospheric gas on substrate = approximately 0.045 m / sec), 400 ° C. to 500 ° C. Was heated at a rate of 10 ° C./min and reduced at 500 ° C. for 30 minutes, but the reduction of molybdenum oxide (MO ₃ ) to metal molybdenum did not proceed, and molybdenum oxide (MoO ₃ ) A molybdenum oxide coating film according to Comparative Example 2 having a colorless and transparent metal oxide fine particle layer densely filled with metal oxide fine particles mainly composed of ₃ ) was produced.

  Table 1 shows the manufacturing process conditions for the inorganicization and reduction treatment of the molybdenum oxide coating film, and the film quality of the obtained film. Further, various characteristics of the manufactured molybdenum oxide coating film were measured in the same manner as in Example 1, and the results are shown in Table 2.

Comparing the above Examples and Comparative Examples, Examples 1 and 2 and Comparative Examples 1 and 2 were all finally subjected to a reduction treatment at 500 ° C. (3 vol% hydrogen-97 vol% nitrogen atmosphere). However, in Examples 1 and 2, since it passes through dark blue lower molybdenum oxide (MoO _x ; 2 ≦ x <3) generated by mineralization, the metallic luster in which the metal molybdenum fine particles are densely packed is obtained. In contrast, in Comparative Examples 1 and 2, a colorless and transparent molybdenum oxide (MoO ₃ ) was generated by mineralization, so that the metal molybdenum coating was reduced. It can be seen that only colorless and transparent molybdenum oxide coating film densely packed with molybdenum oxide fine particles is obtained without proceeding, and the film resistance is remarkably high (in contrast to 110Ω / □ and 200Ω / □ in Examples 1 and 2). Comparative Example 1, Read the ^{3 × 10 10 Ω / □,} 8 × 10 9 Ω / □, It should be noted, Ω / □ is ohms per square and).

  In comparison between Example 1 and Comparative Example 1, all of them were finally subjected to reduction treatment at 500 ° C. (3 volume% hydrogen—97 volume% nitrogen atmosphere). In Example 1, all wavelengths of visible light were used. In the region (380 to 780 nm), the metal molybdenum coating film has a high reflectance and exhibits a metallic luster, whereas in Comparative Example 1, the reduction to the metal molybdenum does not proceed and the colorless and transparent molybdenum oxide is oxidized. Since only an object coating film was obtained, it has a high reflectance at a wavelength around 450 nm due to the interference action of the oxide thin film with the substrate, but the reflectance is low in other wavelength regions and does not show a metallic luster. Recognize.

  Furthermore, it can be seen that the metal molybdenum coating films of Examples 1 and 2 are excellent in adhesion to a heat-resistant substrate and film strength.

  The metal molybdenum coating film according to the present invention can be formed on various heat resistant substrates at various costs using various coating methods, and the resulting metal molybdenum coating film has high conductivity and excellent adhesion. Since it has film strength, it can be expected to be used for, for example, a back electrode layer of a chalcopyrite thin film solar cell, a wiring electrode of a liquid crystal display or a touch panel, and the like.

Claims (4)

A coating process for forming a coating film by applying a coating solution for forming a metal molybdenum coating film containing an organic molybdenum compound as a main component onto a heat-resistant substrate, and a drying process for drying the coating film to form a dry coating film A method for producing a metal molybdenum coating film, wherein the dry coating film is mineralized and reduced by heat treatment to form a metal fine particle layer containing metal molybdenum as a main component. There,
In the heat reduction step, the dry coating film mainly composed of the organomolybdenum compound formed in the drying step is first subjected to a heat treatment at 250 to 350 ° C. to heat the organic components contained in the dry coating film. Forming a metal oxide fine particle layer densely filled with metal oxide fine particles mainly composed of lower molybdenum oxide (MoO _x ; 2 ≦ x <3) by decomposition or combustion, or mineralization removed by thermal decomposition and combustion Thereafter, a reduction treatment is performed in which the temperature is raised to 450 ° C. or higher in a reducing atmosphere to reduce the lower molybdenum oxide (MoO _x ; 2 ≦ x <3), thereby forming metal fine particles mainly composed of metal molybdenum. Is a step of forming a metal fine particle layer densely filled with metal molybdenum coating film. The said organic molybdenum compound is acetylacetone molybdenum (molybdenum (VI) oxide bis-2,4-pentandionate) [MoO ₂ (C ₅ H ₇ O ₂ ) ₂ ]. A method for producing a metal molybdenum coating film.   The reducing atmosphere is an atmosphere comprising hydrogen gas or a neutral gas containing at least one of hydrogen gas or organic solvent vapor, and the neutral gas is at least one of nitrogen gas and inert gas. The method for producing a metal molybdenum coating film according to claim 1 or 2, wherein:   The coating method for forming the metal molybdenum coating film on the heat resistant substrate in the coating step is an inkjet printing method, a screen printing method, a gravure printing method, an offset printing method, a flexographic printing method, a dispenser printing method, a slit coating method. The metal molybdenum coating film according to any one of claims 1 to 3, wherein the coating film is any one of a die coating method, a doctor blade coating method, a wire bar coating method, a spin coating method, a dip coating method, and a spray coating method. Manufacturing method.

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